In a conventional 2-pole single-phase induction motor, a main winding and an auxiliary winding are arranged concentrically and inserted in slots of a stator iron core formed by laminating steel sheets. The main winding and the auxiliary winding are wound with a mechanical angle (hereinafter, a winding inserting angle) which is an inserting angle of 90 degrees or other than 90 degrees according to the required characteristics.
Even if all of the slots have the same cross section area or if at least two kinds of cross section area of the slots are included, when the arrangement of the slots has an axis of symmetry, the number of windings in the slots results in large differences. Consequently, there is a problem that occupying rate of winding (a rate of cross section area of winding occupied in a slot area) of each slot results in large differences.
Then, in a motor of which the winding inserting angle is other than 90 degrees, a stator iron core of a 2-pole single-phase induction motor has been proposed, which is structured to have a group of plural slots having at least three kinds of cross section areas and further the arrangement of the group of slots does not have an axis of symmetry in order to provide a 2-pole single-phase induction motor in which the cross section areas of the slots are effectively utilized to improve its characteristics (see the Patent Document 1, for example).    Patent Document 1: JP03-265448